A coxpobatioet of illiktois



T. G. MARTIN.

REPS/STER ma AUTOMATIC TELEPHONE SYSTEMS.

APPLICATION FILED FEB. 9| 'I9l6. QI, 931 @4540 Patentedug. 26,191.9.

3 SHEETS-SHEET I.

T. G. MARTIN.

REPEATEH FOR AUTOMATIC TELEPHONE sYsEMs.

APPLICAUON FILED FEB. 9, 1916.

Patented Aug. 26, 1919.

3 SHEETS-SHEET 2.

29 0J 6,9 a, P'Pa/ T. G. MARTIN.

REPEATER FOR AUTOMATIC TELEPHONE SYSTEMS.

APPLICATION FILED FEB. 9,1916.

1 ,3 1 4,454 Patented Aug. 26, 1919.

SSHEETS-SHEET 3.

8a @me .l E IIIIIIIIHI wwwa/Md HUT my" TALBOT G. 'MARTI'.N, 0F CHICAGO,ILLINOIS, ASSIGNOR T0 .AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS,A CORPORATION OF ILLINOIS.

maratea..

Specification of Letters Patent.

Patented Aug. 26, 1919.

Application led February 9, 1916. Serial No. 77,247.

To all whom t may concern:

Be it known that l, TALBOT G. MARTIN, a citizen of the United States ofAmerica, and a resident of Chicago, county of Cook, and State ofIllinois, have invented certain new and useful Improvements in Repeatersfor Automatic Telephone Systems, of which the following is aspecification.

My invention relates to automatic telephone systems and moreparticularly to such systems as comprise a plurality of exchangesbetween which connections may be established through the medium ofautomatic switches. ln these systems the various exchanges areinterconnected or linked together by trunk lines. A calling subscriberin one exchange, desiring connection with a subscriber in a secondexchange, manipulates the impulse sending device with which he isprovided to operate a switch or switches at his exchange, whereby atrunk line is selected which extends to the desired second exchange. Atthe second exchange certain automatic switches are accessible to thetrunk line whereby the connection may be extended through to the line ofthe desired subscriber.

It is customary, inv order to obviate the necessity of using more thantwo conductors in a trunk line and in order to secure eiiicienttransmission of the operating impulses, to insert a so-called repeaterin each trunk line. A repeater in common use consists essentially of apair of bridges across the trunk line, the two conductors of which havetheir metallic. continuity broken between the bridges by means ofcondensers. The first bridge contains a controlling relay which operateswhen the trunk is seized to ground thethird conductor iii the well lmownmanner, and to close a circuit including the other bridge which extendsto the distant exchange. controlling relay will be repeated in thecircuit to the distant exchange in a manner readily apparent.,

it will be clear without going into further details that in order tosecure an ecient talking circuit by way of a trunk line and repeater,the capacity of the condensers and the impedance of the bridges must beas high as is practicable. The impedance of the second bridge may 'bemade high without trouble but the impedance ofthe controlling relaybridge and the capacity ot' the con- Interruptions of the circuitof the4densers are both limited by certain features incidental to the sendingof operating impulses over the trunk line, as will appear more. clearlyhereinafter.

lt is the principal object of my invention to provide, in a repeaterhaving condensers.

of moderate capacity and a controlling relay designed to secure the mostecient operation without regard to high impedance, means whereby thecapacity of the condensers and the impedance of the controlling relaybridge may both be increased duringl conversation.

Further objects relate to the circuit arrangements by which theprinciples cf my invention are incorporated into repeaters of well knowntype yand construction to form a simple and eicient apparatus.

To accomplish the foregoing and other useful ends my invention comprisesmeans which will be hereinafter set forth and fully explained, referencebeing had to the accompanying drawings.

In the drawings, Figures 1, 2 and 3, taken in order with the lines atthe ends thereof in `alinemeiit, represent diagrammatically a completecircuit connection between a calling substation A and a calledsubstation A',

the two substations terminating in separate exchanges in a systemembodying the'principles of my invention. The said connection has beenestablished through the medium of the` individual line switch C,selector switch E, repeater F, trunk line Z8- 79, selector switch E',and connector switch H.

Referring now to Fig. 1, the substation A. may be of any suitable orapproved type, and as herein represented comprises the receiver 3,transmitter 4, ringer 5, and condenser 6. Being an automatic substation,it is also provided with an impulse sending device which may be of thetype disclosed in British patent to S. G. S. Dicker, No. 20,654 of 1910.rlhe impulse sending device consists essentially of the impulse springs7 controlled by the impulse wheel 8 through the medium of a finger holedial (not shown).

lThe individual line switch C and the master switch D are of the generaltype of line and mastei` switches disclosed in British patent to R. W.James, No. 26,301 of 1906; being, however, more nearly of the particulartype disclosed in British patent to T. G. Martin, No. 1419 of 1910.Among other details the line switch C comprises a plunger (not shown)attached to a so called plunger arm controlled by the magnet,I 10. Themagnet 10 has two windings, a ull-in winding 13 and a cut-oil or holdingwlnding 12. The pull-in winding, when energized, is strong enough tooperate both the plun er arm 9 and the cut-off armature 11; Whi e thecutofi' winding 12 isonly strong enough to operate thecutfoff armatureand to maintain the plunger arm 9 in an operated osition after it hasbeen operated by the pu l in winding 13. The latter winding iscontrolled through the medium of the line relay 14 which in turn iscontrolled from the substation A. When the plunger arm is operated, theplunger is forced into a bank of contact springs, forcing the springs15, 16, 17, and 18 into engagement, respectively, with contacts 19, 20,21, and Although only one set of springs and contacts (l5-22, inclusive)is shown, it is understood that each line switch is provided with aplurality of such sets, each set forming the terminal of a trunk lineextending to a selector switch. Each trunk line is connected in multipleto corresponding terminals in the banks of all the line switchescontrolled by the master switch D. The function of the master switch, asis well known, is to maintain the plungers of all idle line switches ofits group in position be fore the terminals of an idle trunk line.

The selector switch E is 0f the general type of selector switchdisclosed in United States Letters Patent No. 815,321, granted March 13,1906, to Keith, Erickson and Erickson; being, however, of the particulartype shown in British patent to the Automatic Telephone lManufacturingCompany,

No. 2543 of. 19111. Among other details the selector E comprises a bankof contacts arranged in horizontal rows or levels, which contacts areadapted to be engaged by a set of wipers 23, 24, and 25 carried upon ashaft (not shown) which has a vertical movement controlled by thevertical magnet 27, and a rotary movement controlled by the rotarymagnet 28. The operation of the various parts of the switch iscontrolled through the medium of the double wound line relay 26. Meansifor permitting the switch to be restored to normal position is providedin the release magnet l120, which, upon energizing, withdraws theretaining pawls from the shaft. rlhe contacts 74 and 77 make againsttheir respective springs only when the shaft has been raised one or moresteps from its lowest position. The relays 30 and 32 are slow acting,that is, they retain their armatures for an instant after theirenergizing circuits are broken.

The repeater F (Fig. 2) is of the general type of repeater disclosed inUnited States Letters Patent No. 1,136,912, granted April 20, 1915, toT. G. Martn. The circuits are modified, how ver, and certain parts areadded in orde' to enable it to operate according to the principles of minvention. The functions ofthe various re ays and the operation will bedescribed in detail hereinafter. I

The trunk line 78--79 terminates at the distant exchange in the selectorswitch E which is in all essential particulars the same as selectorswitch E, already described.

Accessible to the selector E I have shown a connector switch H (F ig. 3)which is of the general type of connector switch disclosed in UnitedStates Letters Patent No. 815,176, granted March 13, 1906, to Keith,Erickson and Erickson; being, however, more nearly of the particulartype shown in .British patent to the Automatic Telephone ment controlledby the rotary magnet 84.

The usual side switch comprising thewipers 115, 116, 117, and 118 iscontrolled by the private magnet in the well known Inanner. Theoperation of the various parts of the switch is controlled through themedium of the double wound line relay 82 which also serves to feedtalking current 4to the calling line. The called line is provided withtalk ing current through the windings of the double wound answeringbridge relay 87 which operates, when energized, to reverse the batteryconnections to the trunk conductors 113 and 114. rlhe ringing relay 102affords means for projecting ringing current over a called line tosignal the called subscriber. Means for permitting the connector to berestored to normal position is provided in the release magnet 86, which,upon energizing, withdraws the retaining pawls from the shaft, andreturns the side switch wipers to their first position. The contacts108a and 109a make against their respective springs only when the shafthas been raised one or more steps from its lowest position. Relays 85and 93 are slow acting.

Substation A and the individual line switch C are similar to substationA and its individual line switch C, which have already been described.

' For supplying operating and talking current I have shown two batteriesindicated by reference characters B and B and each having its positiveterminal grounded. I have shown a generator R for supplying ringingcurrent and an interrupter 103 for intermittently breaking the operatingcircuit of the ringing relay. At Q I have shown a busy signalingmachine.

asiatica eration of a system, embodying the princi-Y ples of myinvention. For the purposes of this explanation it will be assumed thatthe subscriber at substation A in one exchange, desired to establishconnection with the sub scriber at substation A in another exchange.

inasmuch as a great deal of the automatic apparatus shown herein is Oldand well known in the art, having been fully described in thepublications above referred to, its operation will be described in amore or less general manner, the details being given only where theyhave to do with the opera,-`

tion of my invention.

Referring now to Fig. l, the subscriber at substation A, upon removinghis receiver to initiate the call, completes an energizing circuit forthe line relay 14 of the line switch C in an obvious and well knownmanner. Upon attracting its armature, the line relay 14 completes anenergizing circuit for the pull-in winding 13. Thepull-in winding, uponenergizing, attracts the plunger arm 9 and the cut-oit' armature 11; theformer, by means of its plunger, forcingthe springs 153-48, inclusive,into engagement, respectively, with contacts 19--22, inclusive; and thelatter disconnecting the line conductors 1 and 2 from their batteryconnections in the line switch.

By the engagement of springs 15 and 18 with lcontacts 19 and 22,respectively, the line conductors 1 and2 are extended to the doublewound line relay 26 oi' the selector l1. The line relay thereupon isenergized over the previously mentioned circuit through substation Aand, upon attracting its armature, completes a circuit from ground at G7to the slow acting relay 30 and thence to battery B. Relay 30, uponenergizing, com` pletes a holding circuit extendin back to the lineswitch C over the ,following path: ground at G3, contacts springs 31,contact 20, spring 16, and holding winding 12 to battery B. Although thecircuit of the line relay 14 has already been broken it retains itsarmature long enough to allow the above holding circuit to beestablished. A' branch of the holding circuit extends by way oit'conductor 201 to multiple test contacts in the banks of connectorshaving access to the line of substation A where, by a ground potentialon these test contacts, the said line is made busy.

The foregoing operations have all occurred in response to the removal ofthe receiver from the hook. The subscriber at substation A may nowoperate his dial in yaccordance with the iirst digit of the desirednumber, thereby breaking the continuity of his loop a correspondingnumber of times.,I As a result of these interruptions the line relay 26is denergized a like number ot times,

sending an impulse at each denergization from ground at G7 through theslow acting relay 32, and the Vertical magnet 27 in s eries `to batteryB. rlhe vertical magnet, in

Iresponse to these impulses, steps up the shaft until the wipers standopposite the horizontal level in which are located contacts which areterminals of trunk lines extending to the desired exchange. The relay32, being slow acting, retains its armature during the series ofimpulses and closes a circuit for the test relay 33, which latter relayprepares a circuit for the rotary magnet and locks itself from groundG3. At the end of the series of impulses the relay 32 denergizes therebycompleting a circuit for the rotary magnet 28, whereupon the wipers arestarted rotating in search of an idle trunk line. As is well known, therotary magnet interrupts its own circuit and also the locking circuit ofthe test relay 33 at every energization, the contacts in the lattercircuit, however, being short circuited by the test wiper 24 whilepassing over busy or grounded test contacts. As soon, therefore, as thetest wiper 24 arrives at an ungrounded test contact the test relay 33falls back and opens the circuit of the rotary magnet, thereby bringingthe wipers 23 and 25 to rest upon contacts which are terminals of anidle trunk line, represented in this case by conductors 71 and 7 3. As afurther result of the denergization of test relay 33, a circuit iscompleted for the line switching relay 29, which latter relay, uponenergizing, disconnects the extended line conductors 1 and 2 from theline relay 26 and further extends them by way of wipers 23 and 25 andtrunk conductors 71 and 73 to the double wound line relay 37 o-\ therepeater F.

An energizing circuit tor the line relay 37 may now be traced asfollows: ground at G21, right hand winding of relay 37, contact springs59 and 60, trunk conductor 73, subscribers loop, trunk conductor 71,contact springs 57 and 56, and left hand winding of relay 37 to batteryB. Line relay 37, upon attracting its armature, completes a circuit forslow acting relay' 38 as follows: ground at G4, contact springs 49 and43, and winding of relay 38 to battery B. Relay 38, upon energizing,completes a holding circuit extending back to the selector E and theline switch C over the following path:

`ground at GG, contact springs 54 and 53,

conductor 72, and wiper 24 to wire junction 202, where the circuitdivides, one branch extending by way of contact springs 75 and rwinding'of line switching relay 29 to batte; y B, and the other branch extendingby way of contact 74, contact springs 76,`con tact 20, spring 16, andholding Winding 12 of line switch C to battery ,l

Relay 38, in addition to closing the holding circuit just described,prepares a circuit for relay 64 by closing contact springs 52, and alsocompletes a circuit including the left hand winding of relay 62 asfollows: ground at G6, contact springs 54 and 55, and left hand windingof relay 62 to `battery B. It should be mentioned at this point that theleft hand winding of relay 62 is simply a polarizing winding, and may beof German silver wire. Owing to its highv resistance and comparativelyfew turns the polarizing winding does not produce a sufficientmagnetizing eli'ect in the core of relay 62 to enable it to attract itsarmature.

Returning now to the line relay 37, an additional function performed bythis relay is the closure of a. circuit including the linev relay 80 ofthe selector E in the distant eX- change. This circuit may be traced asfollows: ground at G8, lower winding of relay 80, contact springs ofline switching relay 29a, trunk conductor 79, contact springs 47,conta-ct springs 69 and 70, winding of impedance coil 63, right handwinding of relay 62, contact springs 66 and 67, trunk conductor 78,contact springs of line switching relay 29a, and upper winding of relay8O to battery B. Line relay 80, upon energizing completes a circuit forslow acting relay 30a, which relay, upon attracting its armature,prepares circuits for the Vertical and rotary magnets 27a and 28, all ina well known manner. llt will be observed that the relay 62 of therepeater F now has current iowing in its right hand winding as well asin its left hand winding. The direction of current flow in the formerwinding however, is such that its magnetizing edect opposes that of thepolarizing winding; therefore the relay 62-remains inoperative.

The subscriber at substation A may now operate his dial in accordancewith the second digit of the desired number resulting in this case in acorresponding number of denergizations of relay 37 of the repeater F. Ateach denergization relay 37 separates contact springs 47, therebyreproducing the interruptions of its circuit in the `circuit of the linerelay 80 of the selector E. It follows that the selector E will beoperated through the medium of its line relay 80 to raise its wipers71a, 72a and 73a, until they stand opposite the horizontal level ofcontacts which are terminals of trunk lines extending to the desiredgroup of subscribers lines; after which the wipers will be automaticallyrotated to select an idle one of these trunk lines, assumed to be inthis case the trunk line extending to the connector H (Fig. 3).

The operation of selector Ey is substantially the same as that ofselector E and need not be described in full. Upon the cnergization ofthe line switching relay 29 after the selecting operation above meti`1tioned, a circuit is completed for the line relay 82 of the connector Hover the following path: groun'1 at G22, lower winding of relay 82,contact springs 211 and 212, conductor 114, wiper 73, contact springs ofline switching relay 29a, conductor 79, contact springs 47, contactsprings 69 and 70, impedance coil 63, right hand winding of relay 62,contact springs 66 and 67, conductor 78, upper contact springs of lineswitching relay 29, wiper 71a, conductor 113, contact springs 213 and214, and upper winding of relay 82 to battery B. Line re, lay 82, uponenergizing, completes an energizing circuit for slow acting relay 85which relay, upon attracting its armature, prepares a circuit for theVertical magnet in the well known manner and also completes a holdingcircuit for the selector E as follows: ground at G10, contact springs91, conductor 92, wiper 72a, contactsprings 75a, and winding of lineswitching relay 29a to battery B.

lt will be well to return at this point to the repeater F and note itsoperation during impulses. At the first denergization of relay 37 at thebeginning of a series of impulses or interruptions of its circuit, acircuit is completed for the slow acting relay 64 as follows: ground atG4, contact springs 49 and 50, Contact springs 52, and Winding of relay64 to battery B. Relays 38 and 64, being slow acting relays, retaintheir armatures in an operated position during a series of impulses. Atthe end of each series of impulses relay 64 denergizes. Inits operatedposition, relay 64 disconnects the trunk conductors 78 and 79 from theconductors 221 and222, respectively, and from the windings in bridgethereof; and connects them over a dierent path which includes only theContact springs 47 of relay 37 and contact springs 68 and 69 of relay64. In this way the impedance coil 63 and winding of relay 62 areexcluded from the controlling circuit of line relay 80 (and later ofline relay 82) while transmitting operating impulses. During this timealso the right hand winding relay 62 is short circuited by the closureof contact springs 65 and 66 to prevent its possible operation due todischarge of condensers 43 and 44. lnasmuch as the loop including thecondensers 43 and 44 and the impedance 63 is in multiple with thesubscribers loop while sending impulses, the condensers should be ofmoderate capacity so as not to interfere with the operation of relay 37.

The subscriber at substation A may now operate his dial in accordancewith the next digit of the desired number resulting as before indencrgization of the line relay 37 of the repeater'F. Relay 37, throughthe medium of Contact springs 47, reproduces the interruptions of4 itscircuit in the circuit of line relay 82 of the connector H. At eachdenergization the line relay 82 sends an impulse from ground at Gthrough '.the relay 93 and vertical magnet 83 in series, side switchwiper 117 being in its first position. The vertical magnet, in responseto these impulses, steps up the shaft until the wipers 88, 89, and 90stand opposite the horizontal level in which are located contacts whichare terminals of the line of substation A. Relay 93, being slow acting,retainsits armature during a series of impulses and maintains anenergizing circuit for the private magnet 95. At the end of the seriesof impulses relay 93 and private magnet 95 both denergize, the lattercontrolling the side switch wipers in the usual manner to advance themto their second position.

The apparatus is now ready for the transmission of'the final series ofimpulses by the same process as before. Side switch wiper 117 being inits second position, the line relay 82 now sends impulses'to the rotarymagnet 84 and the relay 93 in series,

whereby the wipers 88, 89, and 90 are rotated until they stand uponcontacts 231, 232, and 233, which are terminals of the line ofsubstation A'. The private magnet is controlled as before by relay 93,whereby the side switch Wipers are advanced to their third position (itbeing assumed that the called line was idle).

As side switch wiper 118 comes into its third osition=a circuit iscompleted from groun at G11, by way of side switch wiper 118, wiper 89,contact 232, and holding winding 110 of line switch C to battery B. Uponenergizing, the winding 110 attracts the cut ofl' armature of lineswitch C', thereby disconnecting the lines of substation A from theirconnections in line switch C. Ground potential is also placed upon themultiples of contact 232 1n the banks of other connectors, therebymaking the line of substation A busy to other calls.

By the engagement of side switch wipers 115 and 116 with their thirdposition Contact points, the line conductors 113 and 114 are extendedthrough to the wipers 88 and 90, now in engagement with the lineterminals of the desired line. By the engagement of side switch wiper117, with its third position contact point a circuit is completed forthe ringing relay which circuit includes the interrupter 103. Theringing relay thereupon is operated intermittently to project ringingcurrent out over the line of substation A. to signal the calledsubscriber.

The required connection has now been completed. It remains to be shownhow the response of the called subscriber will bring about the desiredcircuit changes at the repeater F. When the subscriber at substation Aremoves his receiver in response te the ringing of his bell anenergizing circuit is completed in the well known manner for the doublewound back bridge relay 87 (ringing relay 102 being momentarilydeenergized). Upon attracting its armature relay 87 completes an initialenergizing circuit for the ring cut-olf relay 104 as follows: ground atG11, side switch wiper 118, contact springs 107, and winding of relay104 to battery B. Relay 104 upon energizing, opens the ringing relaycircuit at contact springs 105 and also locks itself by closing contactsprings 100.

As an additional result of the energization of back bridge relay 87 theline conductors 113 and 114 are reversed as regards their connectionwith the windings of relay 82. It follows that the direction of currentflow in the previously described circuit including the right handwinding of relay 62 (repeater F) will be reversed. Since the twowindings of relay 62 now. assist each other, relay 62 attracts itsarmature, thereby completing the following circuit: ground at G5,contact springs 51, and winding of relay 39 to battery B. Relay 39, uponenergizing, reverses the conductors 71 and 73, as regards theirconnections with the windings of relay 37 and at the same time insertsthe windings of rela-y 40 in series with the windings of relay 37. Theenergizing circuit of relays 37 and 40 may now be traced as follows:ground at G21, right hand winding of relay 37, upper winding of relay40, conductor 71, previously traced circuit through subscribers loop,conductor 73, lower winding of relay 40, and left hand Winding of relay37 to battery B. Upon energizing, relay 40 connects the condensers 41and 42 in multiple, respectively, with condensers 43 and 44. Condensers41 and 42 may be and preferably are of large capacity. Relay 40 ispreferably of high impedance and its resistance should be regulated sothat the combined resistance of relays 40 and 37 is suited to thetransmitter current requirements of the average substation such assubstation A. It may be mentioned that the limitation of the resistanceof relay 40 is only necessary where the repeater is required to supplytransmitter currentto the calling substation. Where this is -not afeature of the operation relay 40 may be of much higher resistance.

Conversation between the calling and called subscribers may now proceed,the voice currents taking the path shown by the heavy conductors.

When the conversation is finished both subscribers will replace theirreceivers. By the hanging up of the receiver at substation A theenergizing circuit of relays 37 and 40 of repeater F are broken.Relay-37, upon denergizing, breaks the energizing circuit of relay 38and the energlzmg cu'- cluit of line relay 82 of the connector H. As aresult of the denergization of relays 38 and 82 the previously describedholding circuits of line switch C, selector E, and selector E are'broken and all the apparatus, including the connector il, is relead andrestored to normal position in the Well known manner.

Had the called line been busy when called, the side switch Wipers of theconnector H would have been locked in their second position immediatelyafter the transmission of' the iinal impulse in order to preventconnection-With the called line and to facilitat/e the application ofthe busy tone to the calling line. Upon receiving the busy signal thecalling subscriber replaces bis receiver, whereupon the apparatus isrestored to normal as before mentioned.

lt will be ses i from the foregoing that l have devised a simple andeicient improvement in repeaters or the general type disclosed herein,whereby the impedance ci? the controlling relay bridge of such ref' ersmay be increased and whereby tir really connected trunk condensers auchrepeaters may liave other condens/eis nected in multiple with them, allthe purpose of providing a more eflicient saliring circuit.

While l have described 'in the foregoing a certain specific embodimentof my i.n-7en tion, il' do not Wisii to be lield strictly to the exactform disclosed, for various adaptations will no vdenbt suggestthemselves to persons skilled in the art. l desire, there tore,tcinclude and have protected by letters Patent all forms andmodifications of my invention which may come Within Le scope oi theappended claims.

What l claim as my invention is:

l. ln a telephone system, a trunk line, a repeater in said trunlr :torre ing impulses over the same, a bridge or said repeater consisting ciarelay and means for automatically adding another relay in with said rstrelay to increase the impedance ci said bridge. f

2. ln a telephone system, a trunk line, a repeater in said trunk forrepeating impulses over the same, capacity in said trunlr,

and means for automaticallyl increasing said capacity.

3. ln a telephone system, a trunk line, a repeater in said trunk forrepeating il pulses over the same, capacity in said trunlr at saidrepeater, and means controlled by said repeater for increasing saidcapacity.

Ll. ln a telephone system, a trunlr line, a repeater in said trunk forrepeating iinpulses over the same,'impedance and capacity in said trunk,and automatic means for increasing said impedance and capacity.

ln a telephone system, a line,

a repeater in said trunk for repeating impulses over the same, impedanceand capacity in said trunk, and automatic means for iirst increasingsaid impedance and for then increasing said capacity.

6. In a telephone system, a trunk line, a.. repeater in said trunk forrepeating impulses over the same, a front bridge and a back bridge forsaid repeater, means for increasing the resistance of said iront bridgeand means for shunting the resistance of said back bridge.

7. ln a telephone system, a called lne, a trunk line, a repeatercomprising a relay in said trunk for repeating impulseJ over the same, abridge for said repeater, and means for automatically adding anotherrelay in series with said first relay to increase the impedance of saidbridge, said means controlled by the called line.

8. ln a telephone system, a called line, a trunk line, a repeater insaid trunk for repeating impulses over the same, capacity in said trunk,means for increasing the capacity of said trunk controlled by the calledline..

ln a telephone system, a. called line, trunk line, a repeater in said'trunk for epeating impulses over the same, capacity n said trunk. atsaid repeater, 'means con- 'rclled by said repeater for increasing tliecapacity of said trunk, said means con trolled by tlie called line.

itl. ln a teiephone system, a called line, a trunk line, a repeater insaid trunk ier repeating impulses ever the same, impedance and capacityin said trunlr, and means tot; increasing the impedance and capacitycdntrolled by tbe calied line.

il. ln a telephone system, a called line, a trunk line, a repeater insaid trunk for repeating impulses over the saine, imped ance andcapacity in said trunk, means for first increasing said impedance andfor tlien increasing said capacity controlled by tbe called line.

12. lny al telephone system, a called line,

a trunk line, a repeater in said trunk for repeating impulses @ver thesaine, imperie ance and capacity in said trunk, means Yfor' increasingsaid impedance controlled by the called line, and means controlled bysaid impedance for increasing said capacity.

'13. ln a telephone system, a called line, a trunk line, a repeater in.said trunk for repeating impulses over the same, a front bridge and aback bridge for said repeater,

said bridges having impedance, means ccntrolled by said called line forincreasing the impedance or said front bridge, and means for removingthe impedance ci@ said back bridge.

ld. ln a telephone system, a called line, trunk line, a repeater in saidtrunk repeating impulses over the same, a front bridge and a back bridgefor said repeater, said bridges having impedance, means for increasingthe impedance of said front bridge, and means controlled by said callingline for removing the impedance of said back bridge.

l5. In a telephone system, a called line, a trunk line, a repeater insaid trunk for repeating impulses over the same, a front bridge and backbridge for said repeater, means controlled by the calling line, forincreasing the resistance of said front bridge and means for shuntingthe resistance of said back bridge.

16. In a telephone system, a calling line, a trunk line, a repeater insaid trunk for repeating impulses over the same, a front 'bridge and aback bridge for said repeater, means for increasing the resistance ofsaid front bridge, and means controlled by the calling line for shuntingthe resistance of said back bridge. Y

I7. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeating impulses over the same, a bridge for said repeater, andmeans responsive to the reversal of said battery current orincreasingthe impedance of said bridge.

18. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeating impulses over the same, capacity in said trunk, and meansresponsive to the reversal of said battery current for increasing thecapacity of said trunk.

19. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeating impulses over the same, capacity in said trunk at saidrepeater, and means controlled by said repeater for increasing thecapacity of said trunk responsive to the reversal of battery current.

20. In a telephone system, a central sourcey of current for operatingand talking purposes, a trunk line, a repeater in said trunk forrepeating impulses over the same, impedance'and capacity in said trunk,means responsive to the reversal of said battery current for increasingsaid impedance and capacity. i

21. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeating impulses over the same, impedance and capacity in saidtrunk, and means responsive to the reversal of said battery current forfirst increasing said impedance and for then increasing said capacity. r

22. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeating impulses over the same, impedance and capacity in saidtrunk, means responsive to the reversal of said battery current forincreasing said impedance, and means controlled by said impedance forincreasing said capacity.

23. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeatin impulses over the same, a front bridge and a back bridgefor said repeater, said bridges having impedance, means responsive tothe reversal of said battery current for increasing the impedance ofsaid frontbridge, and means for removing the impedance of said backbridge.

'24. In a telephone system, a central source of battery current foroperating and talking purposes, a trunk line, a repeater in said trunkfor repeating impulses over the same, a front bridge and a back bridgefor said repeater, means responsive to the reversal of said batterycurrent for increasing the resistance of said front bridge, and meansfor shunting the resistance of said back bridge.

25. In a telephone system, a trunk line, a repeater in said trunk for reeating impulses over the same, a front ridge com--` prising a line relayfor said repeater, a second and a third relay for said repeater, meanscontrolled by said second relay for reversing the connections to saidline relay and for including said third relay in serial relationtherewith.

26. In a telephone system, a trunk line, a repeater in said .trunk forrepeating impulses over the same, a front bridge comprising a line relayfor said repeater, a second and a third relay for said repeater, meanscontrolled by said -second relay for reversing the connections to saidline relay and for includin said third relay in serial relation therewitcondensers in said trunk line, other condensers associated with saidtrunk line, an'd means controlledlby said third relay for including saidother condensers in multiple with 'said lirst mentioned condensers.

27. In a tele 'hone system, a trunk line, a repeater in sai trunk forrepeating impulses over the same, a front bridge and a back bridge forsaid repeater across said trunk, a relay in said front bridge,eondensers between said bridges, and means controlled by said backbridge for changing the relation of said front bridge with respect tosaid trunk and for adding another relay in said front bridge.

28. In a telephone system, a trunk line, a repeater in said trunk forrepeating impulses over the same, a front brldge and `a back bridge forsaid repeater across said trunk, a relay in said front bridge,condensers between. said bridges, and means controlled by said backbridge for reversing the connections of said relay with respect to saidtrunk and for including another relay in said front bridge.

29. In a trunking system, a line, a trunk for setting up a connectionwith said line, capacity in said trunk, and automatic means for varyingthe said capacity.

30. In a trunking system, a line, a trunk for setting up a connectionwith said line, capacity in said trunk, and automatic means for varyingthe said capacity, said automatic means controled for that purpose bysaid line.

3l. In a trunking system, a line, a trunk for setting up a connectionwith said line, capacity in said trunk, automatic means for varying thesaid capacity, said automatic means controlled for that purpose by saidline, another line, and means for connecting said trunk and said otherline. i

32. in a trunking system, a line, a trunk for setting up a connectionwith said line, capacity in said trunk, automatic means for varying thesaid capacity, said automatic means controlled for that purpose by saidline, another line, and means for connecting said trunk and said otherline, whereby said two lines may be connected.

33. In a trunking system, a line, a twoconductor trunk for setting up aconnection with said line, capacity in said trunk conductors, andautomatic means for varying the said capacity.

34:. In a trunking system, a line, a twoconductor trunk for setting up aconnection with'said line, capacity in said trunk conductors, andautomatic means for varying the said capacity, said automatic meanscontrolled for that purpose by said line.

35. In a trunking system, a line, a twoconductor trunk for setting up aconnection with said line, capacity in said trunk conductors, automaticmeans for varying the saidV capacity,. said automatic meanscontrolledfor that purpose by said line, another line, and means forconnecting said trunk and said other line.-

'36. in a trunking system, a line, a twoconductor trunk for setting up aconnection with said line, capacity in said trunk conductors, automaticmeans for varying the said capacity, said automatic means controlled forthat purpose by said line, another ime, means for connecting said trunkand .saidother line, whereby said two lines may be connected.

37Qn a' trunking system, a line; a twoconductor link tor setting up aconnection with said line, capacity in one of said conductors, animpedance-bridge across said conductors, and automatic means forvaryasienta ing said capacity and the impedance of said bridge. l

38.' In a trunking system, a line, a twoconductor link for setting up aconnection with said line, capacity in one of said conductors, animpedance-bridge across said conductors, and automatic means for varyingsaid capacity and the impedance of said bridge, said automatic meanscontrolled for that purpose by said line.

39. n a trunking system, a line, a twoconductor link for setting up aconnection with said line, capacity in one of said conductors, animpedance-bridge across said conductors, automatic means for varyingsaid capacity and the impedance of said bridge, said automatic meanscontrolled for that purpose by said line, another line, and means forconnecting said link and said other line. i

40. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, capacity in one of said conductors, animpedance-bridge across said conductors, automatic means tor varyingsaid capacita7 and the impedance of said bridge, said automatic meanscontrolled for that purpose by said link,'another line, and means forconnecting said link and said other line, wherebv said two lines may beconnected.

41. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, capacity in each of said conductors, animpedance-bridge across said conductors, and automatic means for varyingsaid capacity and the impedance of said bridge. i

'42. In a .trunking system, a. line, a twoconductor link for setting upa connection with said line, capacity in each of' said conductors, animpedance-bridge across `said conductors, and automatic means forvarying said 'capacity and the impedance of said bridge, said automaticmeans controlled for that purpose by said line.

43. In agtrunking system, a line, a twoconductor iink for setting up aconnection with said line, capacity in each of said conductors, animpedance-bridge across said conductors, automatic means for varyingsaid capacity and the impedance of said bridge, said automatic meanscontrolled for that purpose by said line, another line, and means forconnecting said link and said other line.

44. In a trunking system, a line, a two- -conductor link for setting upa connection with said line, capacity in each of said conn ductors, animpedance-bridge across said conductors, automatic means tor varyingsaid capacity and the impedance of said bridge, said automatic meanscontrolled for that purpose by said line, another line, and

lio

means for connecting said link and said other line, whereby said twolines may be connected.

I5. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the. same, another relay, automatic means for inserting saidother relay in saidbridge, capacity in one of said conductors, and meanscontrolled by one of said relays for varying said capacity.

46. In a trunkin'g system, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in one of said conductors, andmeans controlled by one of lsaid relays for varying said capacity,saidautomatic means controlled for that purpose by said line.

47. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in one of said conductors, meanscontrolled by one of said relays for varying said capacity, saidautomatic means controlled for that purpose by said line, another line,and means for connecting said link and said other line.

48. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in one of said conductors, meanscontrolled by one of said relays for Varyingsaid capacity, saidautomatic means controlled for that purpose by said line, another line,and means for connecting said link and said other line, whereby said twolines may be connected.

49. In a trunking system. a line, a twoconductor link Jfor setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in one of said conductors, meanscontrolled by one of said relays for varying said capacity, saidautomatic means controlled for that purpose by said line, another line,and means for connecting said link and said other line, whereby said twolines may be connected, said first relay controlled over said otherline.

50. In a trunking system, a line, a. twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in said link, and means controlledby one of said relays for varying said capacity.

51. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said linkfor'controlling the same, another relay, automatic means for insertingsaid other relay in said bridge, capacity in said link, and meanscontrolled by oneof said relays for varying said capacity, saidautomatic means controlled for that purpose by said line.

52. In a trunking system, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in said link, means controlled byone of said relays for Varying said capacity, said automatic meanscontrolled for that purpose by said line, another line, and means -forconnecting said link and said other line.

53. In a trunking system, a line, a twoconductor link for setting up a.connection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic vmeans for inserting saidother relay in said bridge, capacity in said link, means controlled byone of said relays for Varying said capacity, said automatic meanscontrolled for that purpose by said line, another line, and means forconnecting said link and said other line, whereby said two lines may beconnected.

54. In a trunkingsystem, a line, a twoconductor link for setting up aconnection with said line, a relay bridged across said link forcontrolling the same, another relay, automatic means for inserting saidother relay in said bridge, capacity in said link, means controlled byone of said relays for varying said capacity, said automatic meanscontrolled for that purpose by said line, anlink and said other line,whereby said two lines maybe connected, said first relay controlled oversaid other line.

55.. In a telephone system, a first circuit, a second circuit, a relayin said first circuit` a relay in said second circuit, condensers forinductively connecting said circuits, other condensers, and means underthe control of said second relay for connecting said other condensers inmultiple with said first con- 'densers 56. In a telephone system, afirst circuit, a second circuit, a relay in said first circuit, a relayin said second circuit, condensers for inductively connecting saidcircuits, other condensers, means -under the controlof said second relayfor increasing the impedance of said first circuit, and forcorinectingsaid other condensers in multiple with said iirst condensers.

57. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers torinductively connectino' said circuits, other condensers, means undDerthe control of said second relay for connecting said other condensers inmultiple with said first condensers, and means under the control of saidfirst relay for controlling said second circuit.

58. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other condensers, means under thecontro-l of said second relay for increasing the impedance of said firstcircuit, and for connecting said other condensers in multiple with saidfirst condensers, vand means under the control of said first relay forcontrolling said second circuit.

59. In a telephone system, a. first circuit, a second circuit, a relayin said first circuit, a' relay in said second circuit, condensers forinductively connecting said circuits, means under the control of saidsecond relay for increasing the impedance of said first circuit withoutremoving the said first relay therefrom, means under the control of saidfirst relay for controlling said second circuit, and

additional means controlled by said first relay for excluding saidsecond relay from said second circuit.

60. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers'forinductively connecting said circuits, other condensers, means under thecontrol of said second relay for connecting said other condensers inmultiple with said first condensers, means under the control of saidfirst relay for controlling said second circuit, and additional meanscontrolled by said first relay for excluding said second relay from saidsecond circuit.

6l. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other condensers', means under thecontrol of said second relay for increasing the impedanceA of said firstcircuit, and for connecting said other condensers in multiple with saidfirst condensers, means under the control of said first relay forcontrolling said second circuit, and additional means controlled by saidfirst relay for excluding said second relay from said second circuit.

62. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, means under the control of saidsecond relay for increasing the impedance of said first circuit withoutremoving the said first relay therefrom, and means whereby interruptionsof said first circuit are repeated in said second circuit through themedium of said first relay.,

63. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said Second circuit, condensers forinductively connecting said circuits, other condensers, means under thecontrol of said second relay for connecting said other condensers inmultiple with said first condensers, and means whereby interruptions ofsaid first circuit are repeated in said second circuit through themedium of said first relay.

(34. In a telephone system, a first circuit, a second circuit, a relayin said first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other condensers, means under thecontrol of said second relay for increasing the impedance of said firstcircuit, and for connecting said other condensers in multiple With saidfirst condensers, and means whereby interruptions of' said first circuitare repeated in said second circuit through the medium of said firstrelay.

65. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, `a relay in said second circuit., condensers forinductively connecting said circuits, means under the control of saidsecond relay for increasing the impedance of said first circuit, meanswhereby interruptions of said first circuit are repeated in said secondcircuit through the medium of said first relay,

and means under the control of said first relay for closing said secondcircuit over a new path to the exclusion of said second relay.

66. In a telephone system, a first circuit, asecond circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other condensers, means under thecontrol of said second relay for connecting said other condensers inmultiple with said first condensers, means whereby interruptions of saidfirst circuit are repeated in said second circuit through the medium ofsaid first relay, and means under the control of said first relay forclosing said second circuit over a new path to the exclusion of saidsecond relay.

67. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other condensers, means under thecontrol of said second relay for increasing the impedance of said firstcircuit, and for connecting said other condensers in multiple with saidfirst condensers, means whereby interruptions of raid first circuit arerepeated in said second circuit through the medium of said first relay,and means under the control of said first relay for closing said secondcircuit over a new path to thev exclusion of said second relay. v

88. In a telephone systema rst circuit, a second circuit, a relay insaid rst circuit, a

maracas.

relay in said second circuit, condensers for inductively connecting saidcircuits, means under the control of said second relay for increasingthe impedance of said first circuit, means whereby interruptions of saidfirst circuit are repeated in said second circuit through the medium ofsaid first relay, and means under the control of said first relay forclosing said second circuit over a new path to the exclusion of saidsecond relay, said last means effective during the transmission of saidinterruptions. i

69. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other condensers, means under thecontrol of said second relay for connecting said other condensers inmultiple with said first condensers, means whereby interruptions of saidfirst circuit are repeated in said second circuit through lthe medium ofsaid first relay, and means under the control of said first relay forclosing said second circuit over a new path to the exclusion of Saidsecond relay, said last means effective during the transmission of saidinterruptions.

70. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, other eondensers, means under thecontrol of said second lrelay for increasing the impedance 'of saidfirst circuit, and for connecting said other condensers in multiple withsaid first condensers, means whereby interruptions of said first circuitare repeated'in said second circuit through the medium of said firstrelay, and means under the control of said first relay for closing saidsecond circult over a new path to the exclusion of said second relay,said last means effective during the transmission of said interruptions.

71. In a telephone system, a first circuit, a second circuit, relays insaid first circuit having a certain impedance, a relay in said secnndcircuit, condensers for inductively connecting said circuits,- a sourceof current for said circuits, and means under the control of said secondrelay for increasing the impedance of said first circuit withoutremoving any of the relays initially included therein, said second relaynormally inoperative.

72. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, a source of current for saidcircuits, other condensers, and means under the control of said secondrelay for connecting said other condensers in multiple ywith said firstcondensers, said second relay normally inoperative.

73. In a telephone system, a first circuit, a second circuit, a rel-ayin said first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, a source of current for saidcircuits, other condensers, means under the control of said second relayfor increasing the impedance of said first circuit, and for connectingsaid other condensers in multiple with said first condensers, saidsecond relay normally inoperative.

7l. In a telephone system, a, first circuit, a second circuit, a relayin said first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, a source of' current for saidcircuits, means under the control of said second relay for increasingthe impedance of said first circuit, said second relay normallyinoperative, and means associated with said second circuit for reversingthe direction of current flow therein for operatingk said second relay.

75. In a telephone system, a first circuit, a second circuit, a relay insaid first circuit, a relay in said second circuit, condensers forinductively connecting said circuits, a source of current for saidcircuits, other condensers, means under the control of said second relayfor connecting said other condensers in multiple with said firstcondensers, said second relay normally inopera` tive, and meansassociated with said second circuit for reversing the direction ofcurrent flow therein for operating said second relay. 7 6. In atelephone system, a first circuit, a second circuit, a relay in saidfirst circuit, a relay in said second circuit, condensers forinductively connecting said circuits, a source of current for saidcircuits, other condensers, means under the control of said second relayfor increasing the impedance of said firsteeircuit, and for connectingsaid other condens/ers in multi le with said first condensers, saidsecond re ay normally inoperative, and means associated with said secondcircuit for reversing the direction of current flow therein foroperating said second relay.

Signed by me at Chicago, Illinois, this 2nd day of Feb., 1916.

TLBGT G. MARTIN.

